Oracle資料庫 11.2.0.4 EMON程式持續消耗CPU

清風艾艾發表於2019-11-21
Oracle資料庫

    今天遇到一個問題，就是Oracle 11.2.0.4 EMON程式持續消耗CPU。問題現象如圖所示：

    查詢oracle mos發現是Oracle未釋出的BUG9735536（Doc ID 1603844.1）

APPLIES TO:

Oracle Database - Enterprise Edition - Version 11.2.0.1 to 12.1.0.2 [Release 11.2 to 12.1]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Information in this document applies to any platform.

SYMPTOMS

Event Monitor (EMON) slave process is consuming CPU.

Multiple stacks from the process obtained via 

connect / as sysdba

oradebug setospid 1379

or use  the following to find EMON process

In 11g ps -ef | grep EMON

In 12c ps-ef |grep ennn


oradebug SHORT_STACK

have the form

Oracle pid: 43, Unix process pid: 1379, image: oracle@feltux3154 (E000)

_write()+10<-nttwr()+275<-nsntwrn()+111<-nspsend()+935<-nsdo()+4694<-nsfull_sd()+46<-kpcesend()+952<-kponsnd()+392<-kponepms()+1729<-kponprmsg()+405<-kponemn0()+597<-kponemn()+1152<-ksvrdp()+3653<-opirip()+901<-opidrv()+684<-sou2o()+87<-opimai_real()+280<-ssthrdmain()+295<-main()+203<-_start()+108

which indicates it is stuck in a network write.

CAUSE

The cause of this issue has been identified in unpublished enhancement Bug 973553

SOLUTION

The workaround is to kill the emon slave process via

kill -9 ps_id

where ps_id is the process id of the emon slave.

The emon slave will automatically restart when it is next required to do so.

To permanently resolve the issue if the release is 11.2.0.3 or below apply   (Just apply the fix, no need to set any underscore parameters to activate)

The fix for 9735536 is first included in 11.2.0.4 and higher.

In 11.2.0.4 onwards do the following to enable the fix for unpublished Bug 9735536 :

connect / as sysdba

alter system set "_client_enable_auto_unregister"=true scope=spfile

shutdown immediate

startup

REFERENCES

 - EMON SLAVE PROCESS HANGS IN NETWORK WRITE
NOTE:9735536.8  - Bug 9735536 - Enhancement request which allows ability to selectively remove slow clients from Emon Notification mechanism

    如文件，臨時解決方法是查殺EMON重啟該程式，處理後問題例項的CPU使用率立即下降：

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/29357786/viewspace-2665228/，如需轉載，請註明出處，否則將追究法律責任。

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